The present invention relates to telecommunication switching systems and, in particular, to access and services provided at remote sites to a telecommunication switching system.
In the prior art, it has long been recognized that there often exists a need for supplying a small switching network at a remote site to provide telecommunication switching functions for a group of users at that location. It is also well known that it is desirable that this small switching network be controlled by a central business telecommunication switching system so that the users at the remote site are provided the same features and functions as the users co-located with the central business communication system. In general, there is a need for multiple remote networks. The system disclosed in U.S. Pat. No. 5,159,594 provides remote networks serving a plurality of telecommunication terminals and telecommunication trunks controlled by a central business telecommunication system. In this patent, control is established from the central business communication system to each remote network via ISDN channels that may be switched through intervening switching nodes without disturbing the control channels that have been established. The system disclosed in U.S. Pat. No. 5,159,594 does suffer from the disadvantage that all bearer channels switching must be performed by a central switching network on the central business communication system for the establishments of telephone calls. The result is that considerable bandwidth must be utilized to transport the bearer channels back to the central switching system from the remote switching network for switching purposes. The switching must be performed by the central switching network even if the telephone call has been established between two telecommunication terminals that are each connected to the remote switching network.
U.S. Pat. No. 5,764,639 does disclose a system which allows a central business communication system to have limited control over telephones at a remote location where the telephones are interconnected to a key system unit. The remote telephones via the key system unit can call each other directly or obtain a local trunk to a central office via the key system unit. However, the users at the remote site are required to dial different sequences of digits to call a local telephone or gain access to the local trunk verses the digit sequences used when the user is calling telephone or gaining access to a trunk connected directly to the central business communication system. U.S. Pat. No. 5,764,639 does disclose that the interconnection between the remote user and the central business communication system could be via the public telecommunication switching network using analog or ISDN trunking.
The aforementioned problems are solved and a technical advance is achieved in the art by an apparatus and method that allow a central business communication system to handle all aspects of call setup on a remote switch. Advantageously, call control for a telecommunication call set up on a remote switch continues to be handled by the central business communication system; however, the switching of the bearer channels is performed automatically on the remote switch if the telecommunication call is between telecommunication terminals on the remote switch. In addition, if the telecommunication call is between two remote switches, the remote switches will automatically communicate the bearer channels through an interconnecting media without going through the central business communication system.
In addition, when an Internet protocol (IP) such as IETF RFC 791 is utilized to communicate the bearer channels between the central business communication system and the remote switch, multi-frequency dialing tones received from analog telephones connected to the remote switching network are converted to digital information before transmission via the IP communication channels to the central business telecommunication system.
Other and further aspects of the present invention will become apparent during the course of the following description and by reference to the accompanying drawing.